Datasheet

 
SLUS318B – APRIL 1999 – REVISED JANUARY 2002
6
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pin descriptions
AHI, BHI, CHI: Digital outputs used to control the high-side switches in a three-phase inverter. For specific
decoding information reference Table I.
ALOW, BLOW, CLOW: Digital outputs used to control the low-side switches in a three-phase inverter. For
specific decoding information reference Table I.
BRAKE: BRAKE is a digital input which causes the device to enter brake mode. In brake mode all three high-
side outputs (AHI, BHI & CHI) are turned off, while all three lowside outputs (ALOW, BLOW, CLOW) are turned
on. During brake mode the tachometer output remains operational. The only conditions that can inhibit the
low-side commands during brake are UVLO, exceeding peak current, the output of the PWM comparator, or
the COAST command.
COAST: The COAST input consists of a hysteretic comparator which disables the outputs. The input is useful
in implementing an overvoltage bus clamp in four-quadrant applications. The outputs are disabled when the
input is above 1.75 V.
CT: This pin is used in conjunction with the R_TACH pin to set the frequency of the oscillator. A timing capacitor
is normally connected between this point and ground and is alternately charged and discharged between 2.5 V
and 7.5 V.
C_TACH: A timing capacitor is connected between this pin and ground to set the width of the TACH_OUT pulse.
The capacitor is charged with a current set by the resistor on pin R_TACH .
DIR_IN: DIR_IN is a digital input which determines the order in which the HALLA, HALLB, and HALLC inputs
are decoded. For specific decode information reference Table I.
DIR_OUT: DIR_OUT represents the actual direction of the rotor as decoded from the HALLA, HALLB, and
HALLC inputs. For any valid combination of HALLA, HALLB, and HALLC inputs there are two valid transitions;
one of which translates to a clockwise rotation and another which translates to a counterclockwise rotation. The
polarity of DIR_OUT is the same as DIR_IN while motoring, (i.e. sequencing from top to bottom in Table 1.)
GND: GND is the reference ground for all functions of the part. Bypass and timing capacitors should be
terminated as close as possible to this point.
HALLA, HALLB, HALLC: These three inputs are designed to accept rotor position information positioned 120°
apart. For specific decode information reference Table I. These inputs should be externally pulled up to VREF
or another appropriate external supply.
IOUT: IOUT represents the output of the current sense and absolute value amplifiers. The output signal
appearing is a representation of the following expression:
I
OUT
+ ABS
ǒ
I
SNS_I
* I
SNS_NI
Ǔ
5
This output can be used to close a current control loop as well as provide additional filtering of the current sense
signal.
OC_REF: OC_REF is an analog input which sets the trip voltage of the overcurrent comparator. The sense input
of the comparator is internally connected to the output of the current sense amplifier and absolute value circuit.
PWM_NI: PWM_NI is the noninverting input to the PWM comparator.
PWM_I: PWM_I is the inverting input to the PWM comparator.
QUAD: The QUAD input selects between two-quadrant operation (QUAD = 0) and four-quadrant operation
(QUAD = 1) . When in two-quadrant mode, only the low-side devices are effected by the output of the PWM
comparator. In four-quadrant mode both high- and low-side devices are controlled by the PWM comparator.